1. Field of the Invention
This invention relates to brush and weed cutting blades, particularly such blades as are attached to motorized brush and weed cutting implements.
2. Description of Prior Art
Motorized pruning or brush cutting machines using a variety of metal or elastomer cuttting blade attachments are well known and many different blade designs have been offered in a relatively crowded field. With varying degrees of success objectives such as safety, efficiency, longevity, self-sharpening, economy of manufacture and the like have been achieved. However, certain objectives have not been met, but are the focal point of this application.
It can be stated, that existing blade designs fall into two broad categories. One of these is essentially based on bar-type structures, while the other uses the disk as a basic design element.
U.S. Pat. No. 4,938,012 to Klima (1987), illustrates the bar-type, suitable to some degree for both weeds and grasses as well as for light brush. Unfortunately, the flora has to be of fairly light ligneous substance with insignificant cross-sections, or power requirements to sustain essentially flail-like cutting actions (just two per revolution) rise dramatically as toughness and resistance of objects encountered increase. Moreover, the ponderously intermittend cutting action itself imparts shocks to both equipment and operator. The pulsations become exaggerated through even slight imbalances due to wear or damage to the blade. Ultimately, violent vibrations may render the tool inoperable, until balance is again restored.
A somewhat more effective blade design is illustrated in U.S. Pat. No. 4,302,878 to Bonforte (1979). An additional cutting element has been added to engage the targeted flora with a triangular shape. Still, the cutting action is intermittend, the individual blades are too widely spaced even at 5,000 to 6,000 RPM, not atypical of modem equipment, to effect very smooth cutting. Pulsating impacts are again noticeable during the cutting of fairly substantial ligneous plant members and successful use must be restricted mostly to light flora or soft, sap-laden stalks and the like.
Nonetheless, the triangular design represents a commonly used blade despite some shortcomings, although usually in an all-steel version as illustrated by U.S. Pat. No. 3,781,991 to Stratton et al (1971).
Additional reference is made to U.S. Pat. No. 4,250,622 to Houle (1979), in order to show a disk-type blade featuring multiple cutting elements, assuming for the moment the reinforced elastomer material of this fairly complex design is up to the task of successfully engaging heavy ligneous stalks including tree saplings and stout branching, a task not envisioned by the inventor, who evidently favored the novelty of his original elastomer safety design over more rugged all-metal versions.
All-steel construction is evident en U.S. Pat. No. 4,527,382 to Aono (1983) on variously shaped disk derivative designs with multiple cutting elements peripherally dispersed. These designs with their undulating serrated outlines overcome some of the shortcomings of excessive pulsation and vibration and also allow fairly substantial plant members to be effectively engaged.
The Aono designs, as well as many others, are related to if not derived directly from the common peripherally serrated disk blade, in practically universal use since very early days of the Industrial Revolution. Even today, the common round saw blade is still unsurpassed for simplicity of construction, smoothness of operation and sheer cutting efficiency. Its operational smoothness stems primarily from the extremely rapid successive engagement of a multiplicity of cutting elements. Similarly, its high cutting efficiency results from a very aggressive application of many individual cutting elements.
Adaptation of disk-type blades to brush and weed cutting, however, quickly reveales an Achilles heel, such blades do not function well in an axial mode.
The axial mode of operation is defined within this application (and conforming to the usual mounting position of such blades on brush/weed cutting implements) as having a work direction which is parallel to or extensive of the axis of blade rotation. It is therefore at 90 degrees or right angle to the flat forward blade surface (or downward, as the case may be). It is obvious, that this work direction is contra-indicated, even non-sensical for any ordinary disk saw blade with an intended cutting direction radiating always from the disk center and along paths parallel to the surface of the blade.
This latter, naturally correct operational mode for any circular saw blade in common use, will be referred to in this application as the radial mode.
Using a normally constituted peripherally serrated disk blade in work directions other than the intended radial mode on a brush or weed cutting machine, will result in an unsatisfactory outcome due to the blocking action incurred by the surface of the disk. However, since the outstanding qualities of the conventional cutting disk are unsurpassed smoothness and cutting efficiency - if used as originally intended - these qualities should ideally not be curtailed or even deleted, as was done with so many previous designs. Instead, if possible, these original and time-tested attributes should be adapted in a new and novel design allowing their transfer into a multi-directional blade. The specific tailoring of new qualities for a disk-type blade, widely useful for all types of work, is generally dictated by field conditions. The task, for example, to reduce a large, well established tangle of Rubus Villasus (blackberry) is not well dealt with using a conventional disk blade. Invariably, the many vines will be arched and entwined in random juxtaposition. However, any blade able to cut in the radial mode only, is here of little value. The seemingly stubborn vines, although already cut in many places, will remain largely in place, vine clinging to vine in a thorny and altogether still impenetrable thicket. The necessary subsequent handling involves heavy-gloved, unpleasant and time-consuming labor. Also, an ultimate disposal problem for the cut vegetation still remains.
Somewhat better results are obtained with a multiple blade cutter such as a triangular blade or other blades with additional cutting elements. Still, the cutting action is again largely restricted to radial cuts, parallel to the large flats of the blade, or the radial mode. This restriction requires many blade angle shifts to reach new material. Further, unless relatively light ligneous substances encountered facilitate shredding, final results with this type of blade are only marginally superior to the pure disk design. It should be noted, that very substantial branching, saplings etc. cannot be efficiently cut with this type of blade without extraordinary power inputs.
The need, therefore, for a universal type of blade, fully multidirectional and with equal suitability for relatively heavy ligneous members such as branching etc., as well as light plant matter, is apparent. Specifically, a blade is needed which has combined cutting capability in the above defined traditional radial mode, as well as in the axial mode. It should further be able to cut at all other angles to the blade, where both of these modes of operation come simultaneously into action. To make the blade fully multidirectional, an effective rearward axial mode opposite to the axial mode with an added angular or rearward axial diagonal mode to complement the forward diagonal mode capability, is needed. The term diagonal simply denotes angles to either surface of a blade less than 90 degrees. Diagonal modes can be viewed as transitional modes of operation, as for example, during a change over from a purely axial mode to a radial mode. Diagonal mode capability allows uninterrupted cutting and or shredding, as material is encountered at a variety of angles to the blade, without deliberate blade angle adjustment by the operator. A fully multidirectional blade embodying further the unsurpassed smoothness and cutting efficiency inherent in traditionally serrated cutting elements, has further obvious advantages. A pronounced shredding capability, allowing in-situ shredding, has potential long-term (albeit localized) environmental implications, in addition to the immediate practical benefits of reduced labor input.
Some prior art, notably U.S. Pat. No. 3,078,573 to Kern (1962) does have very limited axial mode capability. The limitation, however, stems from the fact that the cutting elements are really a form of bar-type projection raised from a disk-like structure. This hybrid blade has virtually no radial cutting capability to deal with relatively substantial plant members. Thus one feature has merely been traded for another, as also all other disadvantages of bar-type designs are still present.
It may appear obvious and practical to simply use different blades for different tasks. A bar-type blade can be used for light brush and weeds and a disk-blade may be applied to saplings and more substantial branching etc. Unfortunately, nature herself strongly discourages such a tactic by flourishing in often rich abundance and diversity and on all types of terrain, in close proximity, many different species of plants with their distinct physical characteristics. Repeated blade changes under often arduous field conditions will soon become onerous to the operator and not contribute to work efficiency. However, an appropriately designed fully multidirectional blade allowing unimpeded cutting and shredding of both very light as well as relatively heavy plant substances using a combination of axial, radial or diagonal mode engagements will provide good service. This kind of adaptability is especially welcome when the available alternatives to brush clearing are considered which include the use of heavy equipment, defoiliants, fire and even plant chewing domesticated animals. Usually, however, much laborious hands-on action is required, even when assisted with motorized tools. Further, each of the steps is a certain user of fossil fuel energy (even animals need to be transported, usually, and don't do the job completely in any case), therefore a meaningful reduction of energy consumption through in-situ shredding and subsequent mulching has positive environmental implications.
Nonetheless, prior art, as reflected by world markets and by U.S. Patents, reveals no blade or blade assembly having the desired attributes. In particular, all brush and weed cutting blades heretofore known, suffer from one or more of the following disadvantages:
a) Their designs, if based on the bar-type cutter, are severely limited in cutting larger ligneous plant members without application of extraordinary power.
b) Disk-type designs entail severe limitations with respect to in-situ shredding.
c) Neither bar nor disk-type designs possess adequate capability when employed in the herein defined axial mode.
d) Bar-type cutters typically suffer from a lack of smoothness during heavy cutting action due to the severely limited number of individual cutting engagements per revolution.
e) Bar-type cutters dull easily due to the restricted number of available cutting edges.
f) Use of various types of elastomer materials in cutter construction renders these essentially unsuitable for application on heavy ligneous plant members such as saplings or substantial branching.
g) Bar-type cutters are easily imbalanced due to uneven wear or damage and then suffer from vibration which may render them inoperable until balance is again restored.
h) Disk derivative designs with substantial deviation from true circular shapes are net generally compatible with standard shop reclaiming machines.
i) Cutters of all types typically lack any feature to positively limit the depth of cutting engagement, thereby not protecting the powertrain from potential overload conditions encountered particularly during the felling of saplings etc. when binding of the engaged blade frequently occurs.
j) Some designs are unduly complex, requiring highly specialized tooling and cannot be initially economically produced.
k) No design found in prior art has a special feature which assists the blade to remain engaged during some types of operations, thereby facilitating the in-situ shredding process. This unique feature shall be subsequently named a Locating Guide Feature.